Examination of Coking Behavior of Coking Coal and Binder through Characterization Utilizing High Temperature Solvent Fractionation

Abstract

Steel industries need to increase the use of low-grade coals in coke making due to the recent rapid increase in coking coal price. To do so, it is necessary to effectively use binders, and it is desired to develop a theory on how to mix coals and binders effectively. In this work the coal fractionation method proposed by the authors was applied to characterize coals and binders. Three different-rank coals and two binders (HPC developed by Kobe Steel and ASP) that were heat-treated at 400°C in advance were separated into several fractions having different molecular weight by sequential solvent extractions at different temperatures up to 350°C. The chemical and physical properties of each fraction were found to be almost independent of the coal and binder types. Then, it was clarified that the thermoplastic behaviors of the mixture of coals and binders can be explained by focusing on the relative abundance of the fractions in the mixture. It is therefore possible to determine an appropriate mixing ratio of coals and binders to realize the thermoplastic behavior required to obtain high-strength coke. This approach can be expected as a new mixing theory which is applicable even to low-grade coals and newly-developed binders.